1、BRITISH STANDARD BS 5072-3: 1975 Incorporating Amendment No. 1 Methods of test for Sodium fluoride for industrial use Part 3: Determination of fluorine content UDC 661.833.361:546.33161:543.24.062:546.16BS5072-3:1975 This British Standard, having been approved by the ChemicalsIndustry StandardsCommi
2、ttee, was published under the authority ofthe Executive Board on 30September 1975 BSI 11-1999 The following BSI references relate to the work on this standard: Committee reference CIC/24 Draft for comment 72/52985 DC ISBN 0 580 08107 9 Co-operating organizations The Chemicals Industry Standards Comm
3、ittee, under whose supervision this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: British Steel Industry Chemical Industries Association* Department of Health and Social Security Department of Trade a
4、nd Industry* Department of Trade and Industry Laboratory of the Government Chemist* Fertiliser Manufacturers Association Limited Ministry of Agriculture, Fisheries and Food National Sulphuric Acid Association Royal Institute of Public Health and Hygiene Soap and Detergent Industry Association The or
5、ganizations marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the preparation of this British Standard: Aluminium Federation British Ceramic Research Association Royal Institute of Chemistry Society for Analytical Chemis
6、try Society of Chemical Industry Amendments issued since publication Amd. No. Date of issue Comments 5348 March 1987 Indicated by a sideline in the marginBS5072-3:1975 BSI 11-1999 i Contents Page Co-operating organizations Inside front cover Foreword ii 1 Scope 1 2 References 1 3 Principle 1 4 Reage
7、nts 1 5 Apparatus 2 6 Procedure 2 7 Calculation 3 Figure 1 Typical form of steam distillation apparatus for use in determination of fluorine content 4 Publications referred to Inside back coverBS5072-3:1975 ii BSI 11-1999 Foreword This British Standard has been prepared under the authority of the Ch
8、emicals Industry Standards Committee in order to provide methods for the analysis of sodium fluoride. In the drafting of this standard account has been taken of the method adopted by the International Organization for Standardization (ISO) in the preparation of which the United Kingdom has been an a
9、ctive participant. It is intended to provide further methods, in the form of Parts of this standard, as the work of ISO/TC47 Chemistry (and, in particular, ISO/TC47/SC7 Alumina and related compounds) advances. This Part of BS5072 is based on International Standard ISO2833 “Sodium fluoride for indust
10、rial use Determination of fluorine content Modified Willard-Winter method”, modified to take into account the comments made by the United Kingdom during its development, in particular by omitting the alternatives of spectrophotometric titration and distillation using perchloric acid. This standard p
11、rescribes methods of test only, and should not be used or quoted as a specification defining limits of purity. Reference to the standard should be in a form of words indicating that the methods of test used conform to BS5072. A British Standard does not purport to include all the necessary provision
12、s of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 4, an insi
13、de back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS5072-3:1975 BSI 11-1999 1 1 Scope This Part of BS5072 specifies a modified Willard-Winter method for
14、 the determination of fluorine content of sodium fluoride for industrial use by titration with thorium nitrate solution. 2 References The titles of the British Standards referred to in this standard are listed on the inside back cover. 3 Principle The fluorine is separated from a test portion by dis
15、tillation with sulphuric acid. The distillate is titrated with thorium nitrate solution, using as indicator either sodium alizarinsulphonate, with or without methylene blue as masking agent, or methylthymol blue as indicator. 4 Reagents The reagents used shall be of recognized analytical reagent qua
16、lity. Water complying with the requirements of BS3978 shall be used throughout. 4.1 Hydrochloric acid, approximately0.06N solution. Dilute5ml of hydrochloric acid, approximately1.18g/ml, about36% (m/m) solution, with water to1000ml. 4.2 Perchloric acid, approximately N solution. 4.3 Sodium hydroxide
17、, 20g/l solution. Dissolve20g of sodium hydroxide in water and, after cooling, dilute to1000ml. 4.4 Sulphuric acid, approximately23N. Carefully add, in small quantities,200ml of sulphuric acid, approximately1.84g/ml, about98% (m/m) solution, to approximately100ml of water and, after cooling, dilute
18、to300ml. 4.5 Buffer solution. Either of the following may be used: a) pH 2.7 (for use with sodium alizarinsulphonate indicator). Dissolve9.45g of monochloroacetic acid in50ml of N sodium hydroxide solution and dilute to100ml with water; or b) pH 3.4 (for use with methylthymol blue indicator). Dissol
19、ve6.7g of glycine and11g of sodium perchlorate in11ml of the N perchloric acid solution (4.2) and dilute to100ml with water. 4.6 Thorium nitrate, standardized solution approximately0.067N. 1ml of this solution is equivalent to approximately1.3mg of fluorine (F). 4.6.1 Preparation of the solution. Di
20、ssolve10.01g of thorium nitrate hexahydrate Th(NO 3 ) 4 .6H 2 O in water and dilute to1000ml. 4.6.2 Standardization of the solution 4.6.2.1 Preparation of the standard reference solution. Weigh, to the nearest0.1mg, about200mg of analytical reagent grade anhydrous sodium fluoride, previously heated
21、at600 C in a platinum dish and cooled in a desiccator. Transfer, using20ml to30ml of water, into the distillation flask 5.2 a) containing several soda-lime glass balls (2mm to3mm diameter). Stopper the distillation flask and add, through the dropping funnel 5.2 e),50ml of the sulphuric acid solution
22、 (4.4). Carry out the distillation as described in6.3.1. Collect the distillate in a500ml one-mark volumetric flask, complying with the requirements of BS1792, dilute to the mark and mix. NOTEIf analytical reagent grade sodium fluoride is not available, recrystallize the product as follows. Dissolve
23、 about5g of pure sodium fluoride in125ml of water and, after dissolution, filter under vacuum through a small Buchner funnel. Evaporate the solution in a platinum dish down to approximately60ml. Cool to about50 C and separate the sodium fluoride crystals by centrifuging. Wash the crystals three time
24、s by centrifuging with small quantities of cold water. Transfer the product to a platinum dish and dry in an electric oven, with natural draught, controlled at100 5 C. Remove the dish from the oven, cool in a desiccator, grind the product in an agate mortar and sieve it through a sieve with a mesh s
25、ize of3554m complying with the requirements of BS410. Place the sieved sodium fluoride in a platinum dish, heat for2h at600 C, and then allow to cool in a desiccator. 4.6.2.2 Titration. Transfer a50.0ml aliquot portion of the standard reference solution (4.6.2.1) to the beaker (5.5) and titrate by t
26、he procedure described in6.3.2. Towards the end of the titration add the last few drops of the thorium nitrate solution (4.7.1) carefully with vigorous stirring. 4.6.2.3 Blank test. Carry out a blank test at the same time and following the same procedure (distillation according to6.3.1 and titration
27、 according to6.3.2), using the same quantities of all reagents as in the procedure described in4.6.2.1 and4.6.2.2 but omitting the sodium fluoride. 4.6.2.4 Calculation of strength of the solution. The mass, in milligrams, of fluorine (F) corresponding to1ml of thorium nitrate solution is given by th
28、e formulaBS5072-3:1975 2 BSI 11-1999 where 4.7 Sodium alizarinsulphonate, 0.5g/l solution 1) . Dissolve 0.05g of sodium alizarinsulphonate in water and dilute to100ml. 4.8 Methylene blue, 0.5g/l solution 1) . Dissolve0.05g of methylene blue (oxidation-reduction indicator grade) in water and dilute t
29、o100ml. 4.9 Methylthymol blue, 0.5 g/l solution 1) . Dissolve0.05g of methylthymol blue in water and dilute to100ml. 5 Apparatus Ordinary laboratory apparatus and the following are required. 5.1 Steam generator, for example, such as a flask of capacity 3000ml, fitted with a stopper into which are in
30、serted the following three glass tubes a), b) and c) of internal diameter about6mm: a) a vertical recovery bend tube, for introducing steam into the distillation flask 5.2 a) (one limb dipping into the distillation flask); b) a tube for regulating the steam flow, fitted at its outer end with a rubbe
31、r tube complete with a Mohr clip; c) a safety tube, approximately1m long. 5.2 Steam distillation apparatus, borosilicate glass, with ground glass joints. A typical apparatus is shown inFigure 1 and consists of the following components: a) Claisen flask (distillation flask), 250ml capacity, preferabl
32、y having the following dimensions: 1) diameter of central neck:36mm; 2) length of side neck (including the Vigreux column 5.2 b):275mm; 3) distance between side neck and central neck:65mm; 4) diameter of side neck:20mm. b) Distillation column, Vigreux type, preferably having the following dimensions
33、: 1) length of column between the first and last series of indentations:120mm; 2) 11 groups of3indentations, spaced at120 on the circumference, at12mm separations. c) Thermometer sheath. d) Thermometer, covering the temperature range0 C to200 C, with an effective length of approximately250mm. e) Dro
34、pping funnel, Walter type, about100ml capacity, for insertion in the Vigreux column. f) Graham condenser, with an effective length of about400mm, complying with the requirements of BS1848. 5.3 Electrical heater, for heating the distillation flask 5.2 a) up to150 C and capable of being controlled to
35、within1 C. 5.4 pH meter, fitted with a glass electrode. Essential performance requirements are given in BS2586, BS3145 and BS3422. 5.5 Borosilicate glass beaker, 250ml capacity, tall form. 5.6 Burette, 10ml with0.02ml divisions, complying with the requirements of BS846. 5.7 Stirrer, magnetic NOTEAll
36、 glassware should be carefully washed with hot chromic-sulphuric acid mixture, rinsed thoroughly with water and finally with water complying with the requirements of BS3978. 6 Procedure 6.1 Test portion. Weigh, to the nearest0.1mg, approximately 200mg of the dried sample 2)into the platinum crucible
37、. 6.2 Blank test. Carry out at the same time, using the same procedure, a blank test with the same quantities of all the reagents used for the determination, but omitting the test portion(6.1). m 1 is the mass of sodium fluoride contained in the aliquot portion of the standard reference solution (4.
38、6.2.1) taken for the titration (mg); V 1 is the volume of the thorium nitrate solution(4.6.1) used for the titration of the aliquot portion of the standard reference solution (4.6.2.1) taken for the titration (ml); V 2 is the volume of thorium nitrate solution(4.6.1) used for the titration of the bl
39、ank solution (4.6.2.3) (ml); 0.4525 is the conversion factor for sodium fluoride to fluorine. 1) Instead of using the two indicators 4.7 and4.8 (see6.3.2), the sodium alizarinsulphonate solution (4.7) may be used alone. Alternatively the methylthymol blue (4.9), or any other indicator that gives equ
40、ivalent results with the appropriate buffer and in the specified pH range, may be used. 2) See BS5072-4.BS5072-3:1975 BSI 11-1999 3 6.3 Determination 6.3.1 Distillation. Transfer the test portion(6.1), using20ml to30ml of water, into the distillation flask 5.2 a) containing several soda-lime glass b
41、alls (2mm to3mm diameter). Place a500ml one-mark volumetric flask complying with therequirements of BS1792 under the condenser5.2 f) to collect the distillate. Connect the distillation flask 5.2 a) to the condenser 5.2 f) and start the water circulation. Stopper the distillation flask and add, throu
42、gh the dropping funnel 5.2 e),50ml of the sulphuric acid solution (4.4). Using the electrical heater(5.3), heat the distillation flask 5.2 a) until the solution reaches150 C. When the temperature in the distillation flask5.2 a) has reached150 C, pass steam from the generator(5.1) into the distillati
43、on flask so as to maintain the solution at150 1 C and collect approximately400ml of distillate over a period of about90min. Disconnect the distillation flask 5.2 a) from the steam generator(5.1), allowing the steam to escape to the atmosphere, and remove the heater(5.3). Wash the condenser with a je
44、t of water. Dilute the distillate to the mark in the collecting flask and mix. 6.3.2 Titration. Transfer50.0ml of the contents of the collecting flask to the beaker(5.5). Add to the beaker approximately50ml of water and0.50ml of the sodium alizarinsulphonate solution(4.7) and then, in small portions
45、, the sodium hydroxide solution(4.3) until a pink coloration appears (pH of colour change6.6to6.8). Checking by means of the pH meter(5.4), add the hydrochloric acid solution(4.1), drop by drop, until the pH value is between4.9and5.2(yellow coloration of the solution). Add3.0ml of the sodium alizari
46、nsulphonate solution(4.7) and then, still checking with the pH meter(5.4), add the appropriate buffer solution(4.5) in small portions until the pH is3.4 0.1(approximately1ml of buffer solution is required). Add 0.50 ml of the methylene blue solution(4.8) (green coloration of the solution). Place a s
47、mall glass-encased iron bar in the solution and stir vigorously using the stirrer(5.7). Fill the burette(5.6) with the thorium nitrate solution(4.6) and titrate until a blue-violet colour develops. Ensure that the same lighting conditions are used as for the standardization of the thorium nitrate so
48、lution(4.6.2). NOTE 1Carry out the titration in daylight or fluorescent light only. The titration is not to be carried out with the illumination provided by tungsten filament lamps. NOTE 2If the methylthymol blue(4.9) is used as indicator, the pH3.4 buffer solution4.5 b) should be used instead of th
49、e pH2.7buffer solution4.5 a) and pH adjustments should be carried out with the perchloric acid solution(4.2) instead of the hydrochloric acid solution (4.1). 7 Calculation Fluorine (F) content, expressed as a percentage by mass, is given by the formula where m 0 is the mass of the test portion (g); m 2 is the mass of fluorine corresponding to 1 ml of the standardized thorium nitrate solution(4.6) (g); V 3 is the volume of the standardized thorium nitrate solution(4.6) used for the titration of the aliquot portion
